Ethylene/Alpha-Olefin Copolymer and Method for Preparing the Same

ABSTRACT

The present invention provides an ethylene/alpha-olefin copolymer having narrow molecular weight distribution together with a low density and an ultra low molecular weight, minimized number of unsaturated functional groups, and particularly a small amount of vinylidene among the unsaturated functional groups to show excellent physical properties, and a method for preparing the same.

TECHNICAL FIELD Cross-Reference to Related Applications

This application claims the benefit of Korean Patent Application No.2018-0052045, filed on May 4, 2018, in the Korean Intellectual PropertyOffice, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to an ethylene/alpha-olefin copolymerhaving a small number of unsaturated functional groups and showingexcellent physical properties, and a method for preparing the same.

BACKGROUND ART

Olefin polymerization catalyst systems may be classified into aZiegler-Natta and metallocene catalyst systems, and these two highlyactive catalyst systems have been developed in accordance with thecharacteristics of each. The Ziegler-Natta catalyst has been widelyapplied in a commercial process since its invention in the 1950s, but isa multi-site catalyst in which many active sites are coexist and has thecharacteristics of broad molecular weight distribution of a polymer, inaddition, since the composition distribution of a comonomer isnonuniform, there are limitations in securing desired physicalproperties.

Meanwhile, the metallocene catalyst is composed of the combination of amain catalyst having a transition metal compound as a main component anda promoter which is an organometal compound having aluminum as a maincomponent, and such catalyst is a homogeneous complex catalyst and is asingle site catalyst. According to the single site properties, a polymerhaving narrow molecular weight distribution and uniform compositiondistribution of a comonomer is obtained, and according to the structuraldeformation of the ligand of a catalyst and polymerization conditions,the steric regularity, copolymerization properties, molecular weight,crystallinity, etc. of a polymer may be changed.

U.S. Pat. No. 5,914,289 discloses a method of controlling the molecularweight and molecular weight distribution of a polymer using metallocenecatalysts supported by individual supports, but the amount of a solventused for preparing a supported catalyst and preparation time areconsumed a lot, and there is inconvenience to support the metallocenecatalysts used on individual supports.

Korean Patent Application No. 10-2003-0012308 discloses a method ofcontrolling molecular weight distribution by supporting a dinuclearmetallocene catalyst and a mononuclear metallocene catalyst togetherwith an activator on a support and polymerizing while changing thecombination of the catalysts in a reactor. However, such method haslimitations in accomplishing the properties of individual catalysts atthe same time, and a metallocene catalyst part is separated from asupport component of a completed catalyst, thereby inducing fouling in areactor.

Meanwhile, a linear low-density polyethylene is prepared bycopolymerizing ethylene and alpha olefin using a polymerization catalystat a low pressure, and is a resin having narrow molecular weightdistribution and a short chain branch with a certain length without along chain branch. A linear low-density polyethylene film has theproperties of a common polyethylene, high breaking strength andelongation, and excellent tearing strength and falling weight impactstrength, and thus, is increasingly used in a stretch film, an overlapfilm, etc., to which the conventional low-density polyethylene orhigh-density polyethylene is difficult to apply.

However, most linear low-density polyethylene using 1-butene or 1-hexeneas a comonomer is prepared in a single gas phase reactor or a singleloop slurry reactor, and has higher productivity when compared with aprocess using a 1-octene comonomer. However, the properties of such aproduct also are greatly inferior to a case using a 1-octene comonomerdue to the limitations of catalyst technology used and processtechnology used, and the molecular weight distribution thereof isnarrow, and thus, processability is poor.

U.S. Pat. No. 4,935,474 reports a method of preparing polyethylenehaving broad molecular weight distribution by using two or moremetallocene compounds. U.S. Pat. No. 6,828,394 reports a method ofpreparing polyethylene having excellent processability and which isparticularly suitable as a film, by mixing a comonomer having goodbonding properties and a comonomer without them. In addition, U.S. Pat.No. 6,841,631 and U.S. Pat. No. 6,894,128 indicate that polyethylenehaving bimodal or multimodal molecular weight distribution is preparedas a metallocene catalyst in which at least two kinds of metal compoundsare used, and is applicable to the use of a film, a blow molding, apipe, etc. However, such products have improved processability but anonuniform dispersion state by the molecular weight in a unit particle,and extrusion appearance is rough and physical properties are unstablethough under relatively good extrusion conditions.

In such a background, the preparation of an excellent product makingbalance between physical properties and processability is continuouslyrequired, and particularly, a polyethylene copolymer having excellentphysical properties, for example, long-period properties, is furtherrequired.

DISCLOSURE OF THE INVENTION Technical Problem

Accordingly, the present invention is for solving the above-describedlimitations of the conventional art, and providing anethylene/alpha-olefin copolymer having narrow molecular weightdistribution, a small number of unsaturated functional groups and R_(vd)value, showing excellent physical properties, particularly low viscositychange rate after storing for a long time and excellent long-periodphysical properties, showing a little discoloration at a hightemperature, and having excellent stability at a high temperature, and amethod for preparing the same.

In addition, the present invention provides a hot melt adhesivecomposition showing excellent long-period properties, stability at ahigh temperature and adhesive properties, by including theethylene/alpha-olefin copolymer.

Technical Solution

In order to solve the above tasks, according to an embodiment of thepresent invention, there is provided an ethylene/alpha-olefin copolymersatisfying the following conditions i) to iv):

i) viscosity: 6,000 cP to 40,000 cP, if measured at a temperature of180° C.,

ii) molecular weight distribution (MWD): 1.5 to 3.0,

iii) total number of unsaturated functional groups per 1000 carbonatoms: 0.8 or less, and

iv) a R_(vd) value according to the following Mathematical Equation 1:0.5 or less:

$\begin{matrix}{R_{vd} - \frac{\lbrack{vinylidene}\rbrack}{\lbrack{vinyl}\rbrack + \lbrack{vinylene}\rbrack + \lbrack{vinylidene}\rbrack}} & \left\lbrack {{Mathematical}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

(in Mathematical Equation 1, vinyl, vinylene and vinylidene mean thenumber of each functional group per 1000 carbon atoms, measured throughnuclear magnetic spectroscopic analysis).

Advantageous Effects

The ethylene/alpha-olefin copolymer according to the present inventionhas a low density, an ultra low molecular weight, and narrow molecularweight distribution, thereby showing excellent impact strength andmechanical properties. In addition, the ethylene/alpha-olefin copolymeraccording to the present invention has a small number of totalunsaturated functional groups in a polymer and a small vinylidene ratioand a little viscosity change rate according to time to show excellentlong-period properties, and shows a little discoloration at a hightemperature to show improved stability at a high temperature.

Accordingly, if the ethylene/alpha-olefin copolymer according to thepresent invention is applied to a hot melt adhesive composition, theflowability or reactivity of a copolymer is relatively constant invarious process conditions, and reaction efficiency may be improved, andthus, a hot melt adhesive composition having excellent long-periodproperties, stability at a high temperature and adhesion properties, maybe prepared.

BEST MODE FOR CARRYING OUT THE INVENTION

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to limit the presentinvention. The singular forms are intended to include the plural formsas well, unless the context clearly indicates otherwise. It will beunderstood that the terms “comprise” and/or “comprising,” when used inthis specification, specify the presence of stated features, steps,elements or the combination thereof, but do not preclude the presence oraddition of one or more other features, steps, elements or thecombination thereof.

The present invention may have various changes and be embodied invarious forms, and specific embodiments are illustrated and will beexplained in detail below. However, it should be understood that thepresent invention is not limited to a specific disclosure type, butincludes all changes, equivalents and substituents included in the scopeand technical range of the present invention.

1. Ethylene/Alpha-Olefin Copolymer

Hereinafter, the ethylene/alpha-olefin copolymer of the presentinvention will be explained in detail.

An ethylene/alpha-olefin copolymer according to an embodiment of thepresent invention satisfies the following conditions i) to iv):

i) viscosity: 4,000 cP to 50,000 cP, if measured at a temperature of180° C.,

ii) molecular weight distribution (MWD): 1.5 to 3.0,

iii) total number of unsaturated functional groups per 1000 carbonatoms: 0.8 or less, and

iv) a R_(vd) value according to the following Mathematical Equation 1:0.5 or less:

$\begin{matrix}{R_{vd} = \frac{\lbrack{vinylidene}\rbrack}{\lbrack{vinyl}\rbrack + \lbrack{vinylene}\rbrack + \lbrack{vinylidene}\rbrack}} & \left\lbrack {{Mathematical}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

(in Mathematical Equation 1, vinyl, vinylene and vinylidene mean thenumber of each functional group per 1000 carbon atoms, measured throughnuclear magnetic spectroscopic analysis)

The crosslinking between copolymers is carried out by vinyl andvinylidene, including double bonds, and in the ethylene/alpha-olefincopolymer according to an embodiment, the number of unsaturatedfunctional groups in a copolymer may decrease, particularly, the ratioof vinylidene may decrease, particularly, the number of the unsaturatedfunctional groups and R_(vd) conditions may be satisfied through theinjection of an optimized amount of hydrogen together with a catalystwhich will be explained later during polymerization, thereby showingexcellent stability at a high temperature with decreased discoloration,molecular weight and viscosity change rate at a high temperature.

The ethylene/alpha-olefin copolymer according to an embodiment of thepresent invention has a viscosity of 50,000 cP or less if measured at180° C. in conditions satisfying low density properties as describedabove. More particularly, the viscosity of the ethylene/alpha-olefincopolymer may be 40,000 cP or less, 37,000 cP or less, or 35,000 cP orless, and 4,000 cP or more, or 6,000 cP or more, or 7,000 cP or more, or8,500 cP or more.

Particularly, the ethylene/alpha-olefin copolymer according to anembodiment may have a number of unsaturated functional groups includingvinyl, vinylene and vinylidene of 0.8 or less per 1000 carbon atoms inthe copolymer, more particularly, 0.6 or less, or 0.5 or less, or 0.45or less, or 0.40 or less, and 0.1 or more, or 0.2 or more or 0.23 ormore.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment may have a R_(vd) value calculated according to MathematicalEquation 1 of 0.5 or less, more particularly, 0.3 or less, or 0.25 orless, or 0.22 or less, and greater than 0, or 0.1 or more, or 0.15 ormore.

In the present invention, the amounts (or numbers) of the vinyl,vinylene and vinylidene as the unsaturated functional groups in thecopolymer may be calculated from NMR analysis results. Particularly, thecopolymer was dissolved in a chloroform-d (w/TMS) solution, andmeasurement was performed 16 times at room temperature with anacquisition time of 2 seconds and a pulse angle of 45° , using anAgilent 500 MHz NMR equipment. Then, the TMS peak in 1H NMR wascalibrated to 0 ppm, a CH₃-related peak (triplet) of 1-octene at 0.88ppm and a CH₂-related peak (broad singlet) of ethylene at 1.26 ppm wereconfirmed, respectively, and an integration value of the CH₃ peak wascalibrated to 3 to calculate the contents. In addition, each numbercould be calculated based on the integration values of the vinyl,vinylene and vinylidene in 4.5-6.0 ppm region.

In addition, generally, in case of polymerizing two or more kinds ofmonomers, molecular weight distribution (MWD) increases, and as aresult, impact strength and mechanical properties may decrease andblocking phenomenon, etc. may arise. About this, in the presentinvention, an optimal amount of hydrogen may be injected during carryingout polymerization reaction, and the molecular weight and molecularweight distribution of the ethylene/alpha-olefin copolymer thus preparedmay be decreased, and as a result, impact strength, mechanicalproperties, etc. may be improved.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment of the present invention has a density additionally measuredaccording to ASTM D-792 of 0.85 g/cc to 0.89 g/cc in conditionssatisfying the above-described physical properties. Particularly, thedensity may be 0.855 g/cc or more, or 0.86 g/cc or more, or 0.865 g/ccor more, and 0.89 g/cc or less, or 0.885 g/cc or less, or 0.880 g/cc orless.

Generally, the density of an olefin-based polymer is influenced by thekind and amount of a monomer used during polymerization, apolymerization degree, etc., and a copolymer may be largely influencedby the amount of a comonomer. With the increase of the comonomer, anethylene/alpha-olefin copolymer having a low density may be prepared,and the amount of the comonomer capable of being introduced into acopolymer may be dependent on the copolymerization properties of acatalyst, that is, the properties of the catalyst.

In the present invention, a large amount of a comonomer may beintroduced due to the use of a catalyst composition including atransition metal compound having a specific structure. As a result, theethylene/alpha-olefin copolymer according to an embodiment of thepresent invention may have a low density as described above, and as aresult, excellent processability may be shown. More particularly, theethylene/alpha-olefin copolymer may preferably have a density of 0.860g/cc to 0.885 g/cc, more preferably, a density of 0.865 g/cc to 0.880g/cc, and in this case, the maintenance of mechanical properties and theimproving effects of impact strength according to the control of thedensity are even more remarkable.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment of the present invention has molecular weight distribution(MWD) of 1.5 to 3.0. Particularly, the molecular weight distribution maybe 2.5 or less, more particularly, 1.7 or more, or 1.8 or more, or 1.9or more and 2.3 or less, or 2.1 or less, or 2.0 or less.

Meanwhile, in the present invention, the weight average molecular weight(Mw) and number average molecular weight (Mn) are polystyrene conversionmolecular weights which are analyzed by gel permeation chromatography(GPC), and the molecular weight distribution may be calculated from theratio of Mw/Mn.

The ethylene/alpha-olefin copolymer according to an embodiment of thepresent invention may be a polymer with an ultra low molecular weight,which has a weight average molecular weight (Mw) of 15,000 to 45,000g/mol. More particularly, the weight average molecular weight may be17,000 g/mol or more, or 19,000 g/mol or more, and 40,000 g/mol or less,or 37,000 g/mol or less, or 35,000 g/mol or less.

Also, the ethylene/alpha-olefin copolymer may have a melt index (MI) of200 to 1,300 dg/min. Particularly, the melt index may be 400 dg/min ormore, 500 dg/min or more, and 1,200 dg/min or less, 1,000 dg/min orless. The melt index (MI) is a value measured according to ASTM D-1238(Condition E, 190° C., 2.16 kg load).

If the weight average molecular weight and the melt index satisfy theabove-described ranges, its application to a hot melt adhesivecomposition may be suitable, and remarkable improvement ofprocessability may be expected in connection with the viscosity. Thatis, the viscosity affecting the mechanical properties and impactstrength of the ethylene/alpha-olefin copolymer, and processability maybe controlled by controlling the kind of a catalyst used and the amountof the catalyst used during polymerization, and by satisfying aviscosity range along with the above-described conditions, improvedprocessability may be shown while keeping excellent mechanicalproperties.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment of the present invention may have a number average molecularweight (Mn) of 5,000 to 35,000. More particularly, the number averagemolecular weight may be 7,000 or more, or 8,000 or more, or 9,000 ormore, and 30,000 or less, or 25,000 or less.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment of the present invention may have a crystallizationtemperature (Tc) of 45° C. or more. More particularly, thecrystallization temperature may be 50° C. or more, or 51° C. or more,and 60° C. or less, or 58° C. or less, or 56° C. or less. The highcrystallization temperature as described above is due to the uniformdistribution of a comonomer in the ethylene/alpha-olefin copolymer, andwith the temperature range, excellent structural stability may be shown.

In addition, the ethylene/alpha-olefin copolymer according to anembodiment of the present invention may have a melting temperature (Tm)of 60 to 80° C. More particularly, the melting temperature may be 65° C.or more, or 69° C. or more, or 70° C. or more, and 75° C. or less, or74.5° C. or less, or 74° C. or less. With the melting temperature in thetemperature range as described above, excellent thermal stability may beshown.

In the present invention, the crystallization temperature and meltingtemperature of the ethylene/alpha-olefin copolymer may be measured usinga differential scanning calorimeter (DSC). Particularly, the copolymeris heated to 150° C., kept for 5 minutes, and cooled to 20° C. again,and then, the temperature is elevated again. In this case, the elevatingrate and decreasing rate of the temperature are controlled to 10°C./min, respectively, and the results measured in a section where thetemperature is secondly elevated is set to the melting temperature, andthe results measured in a section where the temperature is decreased isset to the crystallization temperature.

In addition, in the ethylene/alpha-olefin copolymer according to anembodiment of the present invention, the alpha-olefin-based monomerwhich is the comonomer may be an olefin-based monomer of 4 to 20 carbonatoms. Particular example may include propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene,1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicocene, and these may beused alone or as a mixture of two or more.

Among them, the alpha-olefin monomer may be 1-butene, 1-hexene or1-octene considering the remarkable improving effects if applied to ahot melt adhesive composition, and most preferably, 1-octene may beused.

In addition, in the ethylene/alpha-olefin copolymer, the amount of thealpha-olefin which is a comonomer may be appropriately selected from arange satisfying the above-described physical property conditions, andmay be particularly greater than 0 and 99 mol % or less, or 10 to 50 mol%.

An ethylene/alpha-olefin copolymer according to another embodiment ofthe present invention satisfies the following conditions i) to vii):

i) viscosity: 4,000 cP to 50,000 cP, if measured at a temperature of180° C.,

ii) density: 0.85 to 0.89 g/cc,

iii) molecular weight distribution (MWD): 1.5 to 3.0,

iv) total number of unsaturated functional groups per 1000 carbon atoms:0.8 or less,

v) a number average molecular weight (Mn): 9,000 to 25,000,

vi) melt index (MI) at 190° C., 2.16 kg load by ASTM D1238: 200 to 1,300dg/min, and

vii) a R_(vd) value according to Mathematical Equation 1: 0.5 or less:

$\begin{matrix}{R_{vd} - \frac{\lbrack{vinylidene}\rbrack}{\lbrack{vinyl}\rbrack + \lbrack{vinylene}\rbrack + \lbrack{vinylidene}\rbrack}} & \left\lbrack {{Mathematical}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

(in Mathematical Equation 1, vinyl, vinylene and vinylidene mean thenumber of each functional group per 1000 carbon atoms, measured throughnuclear magnetic spectroscopic analysis)

2. Method for Preparing Ethylene/Alpha-Olefin Copolymer

Meanwhile, the ethylene/alpha-olefin copolymer having theabove-described physical properties may be prepared by a preparationmethod, including a step of polymerizing ethylene and analpha-olefin-based monomer by injecting hydrogen in 45 to 100 cc/min inthe presence of a catalyst composition including a transition metalcompound of Formula 1 below.

Accordingly, another aspect of the present invention provides a methodfor preparing the ethylene/alpha-olefin copolymer.

In Formula 1,

R₁ is hydrogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20carbon atoms; alkenyl of 2 to 20 carbon atoms; alkoxy of 1 to 20 carbonatoms; aryl of 6 to 20 carbon atoms; arylalkoxy of 7 to 20 carbon atoms;alkylaryl of 7 to 20 carbon atoms; or arylalkyl of 7 to 20 carbon atoms,

R_(2a) to R_(2e) are each independently hydrogen; halogen; alkyl of 1 to20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20carbon atoms; alkoxy of 1 to 20 carbon atoms; or aryl of 6 to 20 carbonatoms,

R₃ is hydrogen; halogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; aryl of 6 to 20carbon atoms; alkylaryl of 6 to 20 carbon atoms; arylalkyl of 7 to 20carbon atoms; alkyl amido of 1 to 20 carbon atoms; aryl amido of 6 to 20carbon atoms; or phenyl which is substituted with one or more selectedfrom the group consisting of halogen, alkyl of 1 to 20 carbon atoms,cycloalkyl of 3 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms,alkoxy of 1 to 20 carbon atoms and aryl of 6 to 20 carbon atoms,

R₄ to R₉ are each independently a metalloid radical of a metal in group14, which is substituted with hydrogen; silyl; alkyl of 1 to 20 carbonatoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbonatoms; aryl of 6 to 20 carbon atoms; alkylaryl of 7 to 20 carbon atoms;arylalkyl of 7 to 20 carbon atoms; or hydrocarbyl of 1 to 20 carbonatoms; where among the R₆ to R₉, adjacent two or more may be connectedwith each other to form a ring,

Q is Si or C,

M is a transition metal in group 4, and

X₁ and X₂ are each independently hydrogen; halogen; alkyl of 1 to 20carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20carbon atoms; aryl of 6 to 20 carbon atoms; alkylaryl of 7 to 20 carbonatoms; arylalkyl of 7 to 20 carbon atoms; alkylamino of 1 to 20 carbonatoms; or arylamino of 6 to 20 carbon atoms.

In case of including the transition metal compound having the structureof Formula 1 above in a catalyst composition and polymerizing ethyleneand an alpha-olefin-based comonomer together with hydrogen, anethylene/alpha-olefin copolymer having a low density and an ultra lowmolecular weight may be prepared as described above. Since thisethylene/alpha-olefin copolymer has the total number of unsaturatedfunctional groups per 1,000 carbon atoms of 0.8 or less and satisfiesthe R_(vd) value of 0.5 or less, excellent stability at a hightemperature including small discoloration, and small change rate ofmolecular weight and viscosity at a high temperature may be shown.

That is, the crosslinking reaction which may be carried out by anunsaturated functional group and an alkyl radical in a copolymer isdominant in vinyl or vinylidene, which has relatively not much sterichindrance among the unsaturated functional groups, viscosity may belargely changed with the progress of the crosslinking reaction,processability may be adversely affected, and as a result, the stabilityat a high temperature may be deteriorated. However, by applying thepreparation method according to an embodiment of the present invention,the ratio of the vinylidene content among the unsaturated functionalgroups may be decreased, and thus, the crosslinking reaction may notarise well, and at last, a copolymer having a little viscosity changerate at a high temperature may be achieved.

The substituents in Formula 1 will be explained more particularly asfollows.

R₁ may be hydrogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20carbon atoms; alkoxy of 1 to 20 carbon atoms; aryl of 6 to 20 carbonatoms; arylalkoxy of 7 to 20 carbon atoms; alkylaryl of 7 to 20 carbonatoms; or arylalkyl of 7 to 20 carbon atoms.

Particularly, R₁ may be hydrogen; alkyl of 1 to 12 carbon atoms;cycloalkyl of 3 to 12 carbon atoms; alkoxy of 1 to 12 carbon atoms; arylof 6 to 12 carbon atoms; arylalkoxy of 7 to 13 carbon atoms; alkylarylof 7 to 13 carbon atoms; or arylalkyl of 7 to 13 carbon atoms.

More particularly, R₁ may be hydrogen or alkyl of 1 to 12 carbon atoms.

R_(2a) to R_(2e) may be each independently hydrogen; halogen; alkyl of 1to 12 carbon atoms; cycloalkyl of 3 to 12 carbon atoms; alkenyl of 2 to12 carbon atoms; alkoxy of 1 to 12 carbon atoms; or phenyl.

Particularly, R_(2a) to R_(2e) may be each independently hydrogen;halogen; alkyl of 1 to 12 carbon atoms; cycloalkyl of 3 to 12 carbonatoms; alkenyl of 2 to 12 carbon atoms; alkoxy of 1 to 12 carbon atoms;or phenyl.

More particularly, R_(2a) to R_(2e) may be each independently hydrogen;alkyl of 1 to 12 carbon atoms; or alkoxy of 1 to 12 carbon atoms.

R₃ may be hydrogen; halogen; alkyl of 1 to 12 carbon atoms; cycloalkylof 3 to 12 carbon atoms; alkenyl of 2 to 12 carbon atoms; aryl of 6 to20 carbon atoms; alkylaryl of 7 to 13 carbon atoms; arylalkyl of 7 to 13carbon atoms; or phenyl which is substituted with one or more selectedfrom the group consisting of halogen, alkyl of 1 to 12 carbon atoms,cycloalkyl of 3 to 12 carbon atoms, alkenyl of 2 to 12 carbon atoms,alkoxy of 1 to 12 carbon atoms and phenyl.

Particularly, R₃ may be hydrogen; halogen; alkyl of 1 to 12 carbonatoms; cycloalkyl of 3 to 12 carbon atoms; alkenyl of 2 to 12 carbonatoms; alkylaryl of 7 to 13 carbon atoms; arylalkyl of 7 to 13 carbonatoms; phenyl; or phenyl which is substituted with one or more selectedfrom the group consisting of halogen, alkyl of 1 to 12 carbon atoms,cycloalkyl of 3 to 12 carbon atoms, alkenyl of 2 to 12 carbon atoms,alkoxy of 1 to 12 carbon atoms and phenyl.

More particularly, R₃ may be hydrogen; alkyl of 1 to 12 carbon atoms; orphenyl.

R₄ to R₉ may be each independently hydrogen; alkyl of 1 to 20 carbonatoms; cycloalkyl of 3 to 20 carbon atoms; aryl of 6 to 20 carbon atoms;alkylaryl of 7 to 20 carbon atoms; or arylalkyl of 7 to 20 carbon atoms.

Particularly, R₄ to R₉ may be each independently hydrogen; alkyl of 1 to12 carbon atoms; cycloalkyl of 3 to 12 carbon atoms; aryl of 6 to 12carbon atoms; alkylaryl of 7 to 13 carbon atoms; or arylalkyl of 7 to 13carbon atoms.

More particularly, R₄ to R₅ may be each independently hydrogen; or alkylof 1 to 12 carbon atoms, and

among the R₆ to R_(9,) adjacent two or more may be connected with eachother to form an aliphatic ring of 5 to 20 carbon atoms or an aromaticring of 6 to 20 carbon atoms; and the aliphatic ring or the aromaticring may be substituted with halogen, alkyl of 1 to 20 carbon atoms,alkenyl of 2 to 12 carbon atoms, or aryl of 6 to 12 carbon atoms.

Particularly, among the R₆ to R_(9,) adjacent two or more may beconnected with each other to form an aliphatic ring of 5 to 12 carbonatoms or an aromatic ring of 6 to 12 carbon atoms; and the aliphaticring or the aromatic ring may be substituted with halogen, alkyl of 1 to12 carbon atoms, alkenyl of 2 to 12 carbon atoms, or aryl of 6 to 12carbon atoms.

More particularly, R₆ to R₉ may be each independently hydrogen ormethyl.

In addition, Q may be Si, and M may be Ti.

X₁ and X₂ may be each independently hydrogen; halogen; alkyl of 1 to 12carbon atoms; cycloalkyl of 3 to 12 carbon atoms; alkenyl of 2 to 12carbon atoms; aryl of 6 to 12 carbon atoms; alkylaryl of 7 to 13 carbonatoms; arylalkyl of 7 to 13 carbon atoms; alkylamino of 1 to 13 carbonatoms; or arylamino of 6 to 12 carbon atoms.

Particularly, X₁ and X₂ may be each independently hydrogen; halogen;alkyl of 1 to 12 carbon atoms; or alkenyl of 2 to 12 carbon atoms.

More particularly, X₁ and X₂ may be each independently hydrogen; oralkyl of 1 to 12 carbon atoms.

The transition metal compound of Formula 1 forms a structure in whichcyclopentadiene fused with benzothiophene via a cyclic type bond, and anamido group ((N—R₁) are stably crosslinked by Q (Si, C, N or P), and atransition metal in group 4 makes a coordination bond. If the catalystcomposition is applied for polymerizing an olefin, a polyolefin havinghigh activity, a high molecular weight and properties such as a highcopolymerization degree at a high polymerization temperature may beproduced.

Further, in the transition metal compound of Formula 1, as the amidogroup (N-Rd is crosslinked by Q (Si, C, N, P), since Q is bonded to asubstituted or unsubstituted phenyl group, more stable crosslinking maybe achieved and electronically excellent stability may be achieved ifmaking coordination bond with a transition metal.

Since the transition metal compound having the above-described structurehas excellent copolymerization properties due to the phenyl group, acopolymer having a low density may be prepared with a smaller amount ofa comonomer with respect to a catalyst which has not a core structurelike the transition metal compound of Formula 1, and at the same time,since a molecular weight degree is excellent and polymerization at ahigh temperature is possible, there are advantages of injecting hydrogenstably.

That is, the transition metal compound is used but an optimized amountof hydrogen is injected during polymerization reaction in the presentinvention, and thus, an ethylene/alpha-olefin copolymer having an ultralow molecular weight, narrow molecular weight distribution and uniformcomonomer distribution may be provided. Due to the electronic/structuralstability of the transition metal compound, the inclusion of hydrogen isadvantageous. Accordingly, termination reaction is performed uniformlyin polymerization reaction due to hydrogen, and effects of preparing acopolymer having narrow molecular weight distribution and an ultra lowmolecular weight may be expected.

Even further particularly, particular examples of the compound ofFormula 1 may include a compound represented by any one among thestructures below, but the present invention is not limited thereto.

Meanwhile, in the preparation of the ethylene/alpha-olefin copolymeraccording to an embodiment of the present invention, the catalystcomposition may further include a promoter for activating the transitionmetal compound of

Formula 1 above.

The promoter is an organometal compound including a metal in group 13,and particularly may include one or more among a compound of thefollowing Formula 2, a compound of the following Formula 3, and acompound of the following Formula 4:

R₄₁—[Al (R₄₂)—O]_(n)—R₄₃   [Formula 2]

in Formula 2,

R₄₁, R₄₂ and R₄₃ are each independently any one among hydrogen, halogen,a hydrocarbyl group of 1 to 20 carbon atoms, and a halogen-substitutedhydrocarbyl group of 1 to 20 carbon atoms, and

n is an integer of 2 or more,

D (R₄₄)₃  [Formula 3]

in Formula 3, D is aluminum or boron, and

each R₄₄ is each independently any one among halogen, a hydrocarbylgroup of 1 to 20 carbon atoms, and a halogen-substituted hydrocarbylgroup of 1 to 20 carbon atoms,

[L-H]⁺[Z(A)₄]⁻ or [L]⁺[Z(A)₄]⁻  [Formula 4]

in Formula 4,

L is a neutral or cationic Lewis acid; H is a hydrogen atom, and

Z is an element in group 13, and A is each independently a hydrocarbylgroup of 1 to 20 carbon atoms; a hydrocarbyloxy group of 1 to 20 carbonatoms; and any one among substituents of which one or more hydrogenatoms are substituted with one or more substituents among halogen, ahydrocarbyloxy group of 1 to 20 carbon atoms, and a hydrocarbylsilylgroup of 1 to 20 carbon atoms.

More particularly, the compound of Formula 2 may be analkylaluminoxane-based compound in which repeating units are combinedinto a linear, circular or network type, and particular examples mayinclude methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxaneor tert-butylalminoxane.

In addition, particular examples of the compound of Formula 3 mayinclude trimethylaluminum, triethylaluminum, triisobutylaluminum,tripropylaluminum, tributylaluminum, dimethylchloroaluminum,triisopropylaluminum, tri-s-butylaluminum, tricyclopentylaluminum,tripentylaluminum, triisopentylaluminum, trihexylaluminum,trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum,triphenylaluminum, tri-p-tolylaluminum, dimethylaluminummethoxide,dimethylaluminumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron or tributylboron, and particularly, maybe selected from trimethylaluminum, triethylaluminum ortriisobutylaluminum.

In addition, the compound of Formula 4 may include a trisubstitutedammonium salt, dialkyl ammonium salt, or trisubstituted phosphonium typeborate-based compound. More particular examples may include atrisubstituted ammonium salt type borate-based compound such astrimetalammonium tetraphenylborate, methyldioctadecylammoniumtetraphenylborate, triethylammonium tetraphenylborate, tripropylammoniumtetraphenylborate, tri(n-butyl)ammonium tetraphenylborate,methyltetradecyclooctadecylammonium tetraphenylborate,N,N-dimethylanilium tetraphenylborate, N,N-diethylaniliumtetraphenylborate,N,N-dimethyl(2,4,6-trimethylanilium)tetraphenylborate, trimethylammoniumtetrakis(pentafluorophenyl)borate, methylditetradecylammoniumtetrakis(pentaphenyl)borate, methyldioctadecylammoniumtetrakis(pentafluorophenyl)borate, triethylammonium,tetrakis(pentafluorophenyl)borate,tripropylammoniumtetrakis(pentafluorophenyl)borate, tri(n-butyl)ammoniumtetrakis(pentafluorophenyl)borate,tri(sec-butyl)ammoniumtetrakis(pentafluorophenyl)borate,N,N-dimethylanilium tetrakis(pentafluorophenyl)borate,N,N-diethylaniliumtetrakis(pentafluorophenyl)borate, N,N-dimethyl (2, 4,6-trimethylanilium)tetrakis(pentafluorophenyl)borate,trimethylammoniumtetrakis(2,3,4,6-tetrafluorophenyl)borate,triethylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,tripropylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,tri(n-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,dimethyl(t-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,N,N-dimethylanilium tetrakis(2,3,4,6-tetrafluorophenyl)borate,N,N-diethylanilium tetrakis(2,3,4,6-tetrafluorophenyl)borate, andN,N-dimethyl-(2,4,6-trimethylanilium)tetrakis-(2,3,4,6-tetrafluorophenyl)borate;a dialkylammonium salt type borate-based compound such asdioctadecylammonium tetrakis(pentafluorophenyl)borate,ditetradecylammonium tetrakis(pentafluorophenyl)borate, anddicyclohexylammonium tetrakis(pentafluorophenyl)borate; or atrisubstituted phosphonium salt type borate-based compound such astriphenylphosphonium tetrakis(pentafluorophenyl)borate,methyldioctadecylphosphonium tetrakis(pentafluorophenyl)borate, andtri(2,6-dimethylphenyl)phosphoniumtetrakis(pentafluorophenyl)borate.

By using such a promoter, the molecular weight distribution of a finallyprepared ethylene/alpha-olefin copolymer may become more uniform, andpolymerization activity may be improved.

The promoter may be used in an appropriate amount so that the activationof the transition metal compound of Formula 1 may be sufficientlyproceeded.

In addition, the catalyst composition may include the transition metalcompound of Formula 1 in a supported state on a support.

If the transition metal compound of Formula 1 is supported on a support,the weight ratio of the transition metal compound to the support may be1:10 to 1:1,000, more preferably, 1:10 to 1:500. If the support and thetransition metal compound are included in the weight ratio range, anoptimized shape may be shown. In addition, if the promoter is supportedtogether on the support, the weight ratio of the promoter to the supportmay be 1:1 to 1:100, more preferably, 1:1 to 1:50. If the promoter andthe support are included in the weight ratio, catalyst activity may beimproved, and the minute structure of the polymer thus prepared may beoptimized.

Meanwhile, the support may use silica, alumina, magnesia or a mixturethereof, or these materials may be used after removing moisture from thesurface by drying at a high temperature, in a state where a hydroxylgroup or a siloxane group, which have high reactivity, are included. Inaddition, the support dried at a high temperature may further include anoxide such as Na₂O, K₂CO₃, BaSO₄ and Mg(NO₃)₂, a carbonate, a sulfate,or a nitrate component.

The drying temperature of the support is preferably, from 200 to 800°C., more preferably, from 300 to 600° C., most preferably, from 300 to400° C. If the drying temperature of the support is less than 200° C.,humidity is too high and water at the surface may react with thepromoter, and if the temperature is greater than 800° C., the pores atthe surface of the support may be combined to decrease the surface area,and a large amount of the hydroxyl groups at the surface may be removedto remain only siloxane groups to decrease reaction sites with thepromoter, undesirably.

In addition, the amount of the hydroxyl group at the surface of thesupport may preferably be 0.1 to 10 mmol/g, and more preferably, 0.5 to5 mmol/g. The amount of the hydroxyl group at the surface of the supportmay be controlled by the preparation method and conditions of thesupport, or drying conditions such as temperature, time, vacuum andspray drying.

Meanwhile, the polymerization reaction of the ethylene/alpha-olefincopolymer may be performed by continuously injecting hydrogen andcontinuously polymerizing ethylene and an alpha-olefin-based monomer inthe presence of the catalyst composition.

In this case, the hydrogen gas restrains the rapid reaction of thetransition metal compound at an initial stage of polymerization andplays the role of terminating polymerization reaction. Accordingly, bythe use of such hydrogen gas and the control of the amount thereof used,an ethylene/alpha-olefin copolymer having narrow molecular weightdistribution with an ultra low molecular weight may be effectivelyprepared.

The hydrogen gas may be injected in 45 to 100 cc/min, more particularly,50 to 95 cc/min. If the hydrogen gas is injected under theabove-described conditions, the ethylene/alpha-olefin polymer thusprepared may accomplish the physical properties in the presentinvention. If the hydrogen gas is injected in an amount less than 45cc/min, the termination of the polymerization reaction may nothomogeneously carried out, and the preparation of anethylene/alpha-olefin copolymer having desired physical properties maybecome difficult, and if the amount is greater than 100 cc/min, theterminating reaction may arise excessively fast, and it is apprehendedthat an ethylene/alpha-olefin copolymer having an excessively smallmolecular weight may be prepared.

In addition, the polymerization reaction may be performed at 80 to 200°C., but by controlling the injection amount of the hydrogen togetherwith the polymerization temperature, the number of unsaturatedfunctional groups in the ethylene/alpha-olefin copolymer and the monomerreactivity ratio may be controlled even more advantageously.Accordingly, particularly, the polymerization reaction may be carriedout at 100 to 150° C., more particularly, 100 to 140° C.

In addition, during the polymerization reaction, an organoaluminumcompound is further injected to remove moisture in a reactor, and thepolymerization reaction may be performed in the presence of thecompound. Particular examples of such organoaluminum compound mayinclude trialkyl aluminum, dialkyl aluminum halide, alkyl aluminumdihalide, aluminum dialkyl hydride or alkyl aluminum sesquihalide, etc.,and more particular examples may include Al(C₂H₅)₃, Al(C₂H₅)₂H,Al(C₃H₇)₃, Al(C₃H₇)₂H, Al(i-C₄H₉)₂H, Al(C₈H17)₃, Al(C₁₂H₂₅)₃, Al(C₂H₅)(C₁₂H₂₅)₂, Al(i-C₄H₉) (C₁₂H₂₅)₂, Al(i-C₄H₉)₂H, Al(i-C₄H₉)₃, (C₂H₅)₂AlCl,(i-C₃H₉)₂AlCl or (C₂H₅)₃Al₂Cl₃. Such an organoaluminum compound may becontinuously injected into the reactor, and for appropriate removal ofhumidity, the organoaluminum compound may be injected in a ratio ofabout 0.1 to 10 mole per 1 kg of a reaction medium injected into thereactor.

In addition, a polymerization pressure may be about 1 to about 100Kgf/cm², preferably, about 1 to about 50 Kgf/cm², more preferably, about5 to about 30 Kgf/cm².

In addition, if the transition metal compound is used in a supportedstate on a support, the transition metal compound may be injected afterbeing dissolved or diluted in an aliphatic hydrocarbon solvent of 5 to12 carbon atoms, for example, pentane, hexane, heptane, nonane, decane,and isomers thereof, an aromatic hydrocarbon solvent such as toluene andbenzene, a chlorine atom-substituted hydrocarbon solvent such asdichloromethane and chlorobenzene, etc. The solvent used herein ispreferably used after removing a small amount of water or air, whichacts as a catalyst poison, by treating with a small amount of alkylaluminum, and a promoter may be further used.

The ethylene/alpha-olefin copolymer prepared by the above-describedpreparation method has narrow molecular weight distribution togetherwith an ultra low molecular weight, and at the same time, the vinylcontent in a polymer may be minimized, and R_(vd) satisfies theconditions of 0.5 or less. Accordingly, excellent physical properties,particularly, excellent stability at a high temperature may be shown,and if applied to a hot melt adhesive composition, processabilitytogether with adhesive properties may be improved.

Therefore, according to another embodiment of the present invention, ahot melt adhesive composition including the ethylene/alpha-olefincopolymer is provided.

The hot melt adhesive composition may be prepared according to a commonmethod except for including the ethylene/alpha-olefin copolymer as amain component, and used.

MODE FOR CARRYING OUT THE INVENTION Examples

Hereinafter, preferred embodiments will be suggested to assist theunderstanding of the present invention. However, the embodiments areprovided only for easy understanding of the present invention, and thecontents of the present invention is not limited thereto.

Synthetic Example: Preparation of Transition Metal Compound

Step 1: Preparation of Ligand Compound (1a-1)

To a 250 mL schlenk flask, 10 g (1.0 eq, 49.925 mmol) of1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophene and 100 mL of THF wereput, and 22 mL (1.1 eq, 54.918 mmol, 2.5 M in hexane) of n-BuLi wasadded thereto dropwisely at −30° C., followed by stirring at roomtemperature for 3 hours. A stirred Li-complex THF solution wascannulated into a schlenk flask containing 8.1 mL (1.0 eq, 49.925 mmol)of dichloro(methyl) (phenyl)silane and 70 mL of THF at −78° C., followedby stirring at room temperature overnight. After stirring, drying invacuum was carried out and extraction with 100 ml of hexane was carriedout.

To 100 ml of an extractedchloro-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophene-3-yl)-1,1-(methyl)(phenyl)silane hexane solution, 42 mL (8 eq, 399.4 mmol) of t-BuNH₂ wasinjected at room temperature, followed by stirring at room temperatureovernight. After stirring, drying in vacuum was carried out andextraction with 150 ml of hexane was carried out. After drying thesolvents, 13.36 g (68%, dr=1:1) of a yellow solid was obtained.

¹H NMR(CDCl₃, 500 MHz): δ 7.93(t, 2H), 7.79(d,1H), 7.71(d,1H), 7.60(d,2H), 7.48(d, 2H), 7.40-7.10(m, 10H, aromatic), 3.62(s, 1H), 3.60(s, 1H),2.28(s, 6H), 2.09(s, 3H), 1.76(s, 3H), 1.12(s, 18H), 0.23(s, 3H),0.13(s, 3H)

Step 2: Preparation of Transition Metal Compound (1a)

To a 100 mL schlenk flask, 4.93 g (12.575 mmol, 1.0 eq) of a ligandcompound of Formula 2-4 and 50 mL (0.2 M) of toluene were put and 10.3mL (25.779 mmol, 2.05 eq, 2.5 M in hexane) of n-BuLi was added theretodropwisely at −30° C., followed by stirring at room temperatureovernight. After stirring, 12.6 mL (37.725 mmol, 3.0 eq, 3.0 M indiethyl ether) of MeMgBr was added thereto dropwisely, 13.2 mL (13.204mmol, 1.05 eq, 1.0 M in toluene) of TiCl₄ was put in order, followed bystirring at room temperature overnight. After stirring, drying in vacuumand extraction with 150 mL of hexane were carried out, the solvents wereremoved to 50 mL, and 4 mL (37.725 mmol, 3.0 eq) of DME was addeddropwisely, followed by stirring at room temperature overnight. Again,drying in vacuum and extraction with 150 mL of hexane were carried out.After dying the solvents, 2.23 g (38%, dr =1:0.5) of a brown solid wasobtained.

¹H NMR(CDCl₃, 500 MHz): δ 7.98(d, 1H), 7.94(d, 1H), 7.71(t, 6H),7.50-7.30(10H), 2.66(s, 3H), 2.61(s, 3H), 2.15(s, 3H), 1.62(s, 9H),1.56(s, 9H), 1.53(s, 3H), 0.93(s, 3H), 0.31(s, 3H), 0.58(s, 3H), 0.51(s,3H), −0.26(s, 3H), −0.39(s, 3H)

[Preparation of Ethylene/Alpha-Olefin Copolymer]

Example 1

Into a 1.5 L autoclave continuous process reactor, a hexane solvent (5.0kg/h) and 1-octene (1.00 kg/h) were charged, and the top of the reactorwas pre-heated to a temperature of 150° C. A triisobutylaluminumcompound (0.05 mmol/min), the transition metal compound (1a) (0.40μmol/min) prepared in the Synthetic Example as a catalyst, and adimethylanilium tetrakis(pentafluorophenyl) borate promoter (1.20μmol/min) were injected into the reactor at the same time. Then, intothe autoclave reactor, ethylene (0.87 kg/h) and a hydrogen gas (50cc/min) were injected and copolymerization reaction was continuouslycarried out while maintaining a pressure of 89 bar and a polymerizationtemperature of 125° C. for 60 minutes or more to prepare a copolymer.

Then, a remaining ethylene gas was exhausted out and thecopolymer-containing solution thus obtained was dried in a vacuum ovenfor 12 hours or more. The physical properties of the copolymer thusobtained were measured.

Examples 2 to 5 and Comparative Examples 1 to 7

Polymers were prepared by carrying out the same method as in Example 1except that the reactant materials were injected in amounts listed inTable 1 below.

TABLE 1 Catalyst Promoter 1-C8 H₂ injection injection injectionPolymerization injection amount amount amount TiBAl temperature amount(μmol/min) (μmol/min) (kg/h) (mmol/min) (° C.) (cc/min) Example 1 0.401.20 1.00 0.05 125 50 Example 2 0.40 1.20 1.00 0.05 125 75 Example 30.40 1.20 1.00 0.05 125 80 Example 4 0.40 1.20 1.00 0.05 125 95 Example5 0.20 0.60 1.10 0.05 125 85 Comparative Example 1 0.70 2.10 2.00 0.05150 0 Comparative Example 2 0.40 1.20 1.00 0.05 125 0 ComparativeExample 3 0.40 1.20 1.00 0.05 125 10 Comparative Example 4 0.40 1.201.00 0.05 125 15 Comparative Example 5 0.40 1.20 1.00 0.05 125 130Comparative Example 6 0.26 0.78 1.20 0.05 125 35 Comparative Example 70.65 1.95 2.20 0.05 160 0 * In Comparative Examples 6 and 7,[Me₂Si(Me₄C₅)NtBu]Ti(CH₃)₂ was used as a catalyst.

[Evaluation of Physical Properties of Olefin Polymer]

Experimental Example 1

With respect to the ethylene/alpha-olefin copolymers prepared in theExamples and the Comparative Examples, physical properties were measuredaccording to the methods described below and are shown in Table 2.

1) Density (g/cm³): measured according to ASTM D-792.

2) Viscosity (cP): measured using a Brookfield RVDV3T viscometer andaccording to the method described below. In detail, 13 ml of a specimenwas put in a specimen chamber and heated to 180° C. using BrookfieldThermosel. After the specimen was completely dissolved, a viscometerequipment was lowered to fix a spindle to the specimen chamber, therotation speed of the spindle (SC-29 high temperature-melt spindle) wasfixed to 20 rpm, and viscosity values were deciphered for 20 minutes ormore, or until the value was stabilized, and a final value was recorded.

3) Viscosity change rate (%): measured using a Brookfield RVDV3Tviscometer and according to the method described below. In detail, 13 mlof a specimen was put in a specimen chamber and heated to 180° C. usingBrookfield Thermosel. After the specimen was completely dissolved, aviscometer equipment was lowered to fix a spindle to the specimenchamber, the rotation speed of the spindle (SC-29 high temperature-meltspindle) was fixed to 20 rpm, and viscosity values were recorded onceper hour for 72 hours. A difference between an initial viscosity and aviscosity after 72 hours was converted into a percentage, and theviscosity change rate was calculated.

4) Melting temperature (Tm, ° C.): The melting temperature of a polymerwas measured using a differential scanning calorimeter (DSC, apparatusname: DSC 2920, manufacturer: TA instrument). Particularly, the polymerwas heated to 150° C., kept for 5 minutes, and cooled to -100° C., andthen, the temperature was elevated again. In this case, the elevatingrate and decreasing rate of the temperature were controlled to 10°C./min, respectively. The maximum point of an endothermic peak measuredin a second elevating section of the temperature was set to the meltingtemperature.

5) Crystallization temperature (Tc, ° C.): performed by the same methodas that for measuring the melting temperature using DSC. From a curverepresented while decreasing the temperature, the maximum point of anexothermic peak was set to crystallization temperature.

6) Weight average molecular weight (g/mol) and molecular weightdistribution (MWD): a number average molecular weight (Mn) and a weightaverage molecular weight (Mw) were measured, respectively, by gelpermeation chromatography (GPC, PL GPC220) under the conditions below,and molecular weight distribution was calculated through dividing theweight average molecular weight by the number average molecular weight:

-   -   Column: PL Olexis    -   Solvent: trichlorobenzene (TCB)    -   Flow rate: 1.0 ml/min    -   Specimen concentration: 1.0 mg/ml    -   Injection amount: 200 μl    -   Column temperature: 160° C.    -   Detector: Agilent High Temperature RI detector    -   Standard: Polystyrene (calibrated by cubic function)

7) Total number of unsaturated functional groups (per 1000 C): thenumbers of vinyl, vinylene, and vinylidene per 1000 carbon atoms weremeasured from the NMR analysis results.

In detail, first, in order to remove remaining 1-octene which may bepresent in a specimen, the polymer was prepared by reprecipitation priorto conducting NMR analysis. In detail, 1 g of the polymer was completelydissolved in chloroform of 70° C., and the polymer solution thusobtained was slowly poured into 300 ml of methanol while stirring toreprecipitate the polymer. The reprecipitated polymer was dried invacuum at room temperature. The above-described process was repeatedonce more to obtain a polymer from which remaining 1-octene was removed.

30 mg of the specimen of the polymer obtained above was dissolved in 1ml of a chloroform-d (w/TMS) solution. Measurement was performed 16times at room temperature with an acquisition time of 2 seconds and apulse angle of 45°, using an Agilent 500 MHz NMR equipment. Then, theTMS peak in 1H NMR was calibrated to 0 ppm, a CH₃-related peak (triplet)of 1-octene at 0.88 ppm and a CH₂-related peak (broad singlet) ofethylene at 1.26 ppm were confirmed, respectively. An integration valueof the CH₃ peak was calibrated to 3 to calculate the contents. Thenumbers of vinyl, vinylene and vinylidene could be calculated based onthe integration values of each functional group in 4.5-6.0 ppm region.For reference, the viscosity of Comparative Example 6 below was too lowviscosity, and was not measured.

8) R_(vd): R_(vd) value was calculated according to the followingMathematical Equation 1 from the numbers of vinyl, vinylene andvinylidene, measured through the NMR analysis:

$\begin{matrix}{R_{vd} - \frac{\lbrack{vinylidene}\rbrack}{\lbrack{vinyl}\rbrack + \lbrack{vinylene}\rbrack + \lbrack{vinylidene}\rbrack}} & \left\lbrack {{Mathematical}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

(in Mathematical Equation 1, vinyl, vinylene and vinylidene mean thenumber of each functional group per 1000 carbon atoms, measured throughnuclear magnetic spectroscopic analysis).

TABLE 2 Viscosity change Number of unsaturated functional groups (per1000 C) Molecular Density Tc/Tm Viscosity rate Total weight (g/cc) (°C.) (cP) (%) amount vinyl vinylene vinylidene R_(vd) Mw distributionExample 1 0.873 50.6/66.5 35000 18 0.40 0.05 0.27 0.08 0.20 34900 1.98Example 2 0.875 52.0/68.1 17000 15 0.35 0.04 0.24 0.07 0.20 24400 1.96Example 3 0.876 52.3/68.9 13500 14 0.32 0.03 0.22 0.07 0.22 22400 1.98Example 4 0.877 53.2/69.7 8500 11 0.29 0.03 0.20 0.06 0.21 19500 1.77Example 5 0.875 52.2/68.3 17000 12 0.30 0.02 0.21 0.07 0.18 24500 1.96Comparative 0.872 49.7/66.0 >50000 N/A 1.36 0.20 0.78 0.39 0.29 468002.14 Example 1 Comparative 0.874 51.5/67.6 >50000 N/A 0.54 0.06 0.380.10 0.19 75400 2.08 Example 2 Comparative 0.874 51.3/67.8 >50000 N/A0.45 0.04 0.32 0.09 0.20 57700 2.09 Example 3 Comparative 0.87350.5/66.3 >50000 N/A 0.42 0.04 0.29 0.09 0.21 48700 2.08 Example 4Comparative 0.879 55.7/72.7 3500 N/A 0.29 — — — — 14600 1.97 Example 5Comparative 0.876 56.1/73.2 13900 22 0.32 0.03 0.10 0.20 0.63 22800 1.94Example 6 Comparative 0.875 55.3/73.1 15800 41 1.38 0.19 0.79 0.40 0.2926700 2.24 Example 7 In Table 2, “—” means not measured, and “N/A” meansunmeasurable.

Referring to Table 2, the ethylene/alpha-olefin copolymers of Examples 1to 5, which were prepared by using the catalyst composition includingthe transition metal compound according to the present invention andinjecting hydrogen during polymerization, showed a low density, at thesame time, an ultralow molecular weight (evaluated by viscosity), narrowmolecular weight distribution when compared with Comparative Examples 1to 7, and the total number of unsaturated functional groups was 0.5 orless per 1,000 carbon atoms and at the same time, a R_(vd) value was 0.5or less, particularly, 0.22 or less.

Particularly, in case of Comparative Examples 1 to 4, in which hydrogenwas not injected or injected in an amount not more than a certainamount, copolymers with a quite high molecular weight were prepared, andmolecular weight distribution was broad and thus, inferior physicalproperties were expected. In addition, the viscosity was high and theviscosity and its change rate were unmeasurable using the SC-29 hightemperature-melt spindle (5000-45000 cP), and the application to a hotmelt adhesive composition is unsuitable. In addition, in case ofComparative Example 2, the R_(vd) value was similar to that of theExamples, but the total number of unsaturated functional groups wasgrater than 0.5, and the deterioration of physical properties thereby isexpected.

In addition, in case of Comparative Example 5, in which an excessiveamount of hydrogen was injected, the polymerization was terminated at anearly stage due to hydrogen and a copolymer having a very smallmolecular weight was prepared. In addition, the viscosity was low andthe measurement of the viscosity change rate using the SC-29 hightemperature-melt spindle (5000-45000 cP) was impossible.

In addition, in case of Comparative Example 7, in which hydrogen was notinjected and a catalyst other than the catalyst according to the presentinvention was applied, molecular weight distribution was relativelybroad, and the total number of unsaturated functional groups was 1.38and was confirmed significant. In case of Comparative Example 6, inwhich hydrogen was injected, molecular weight distribution and viscosityproperties were similar, and the total number of unsaturated functionalgroups was markedly decreased, but the R_(vd) value was relativelyincreased.

This could be affected by the compound used as the catalyst. From theview of beta-hydride elimination of the production process of theunsaturated functional groups, if the polymerization is terminated after1,2-insertion of octene, vinylidene is produced, if the polymerizationis terminated after 2,1-insersion, vinylene is produced, and if thepolymerization is terminated after the insertion of ethylene, vinyl isproduced. If the copolymerization properties of the catalyst areexcellent, 2,1-insersion may also be increased, and accordingly, thevinylene content may tend to increase and the vinylidene content maytend to decrease.

That is, the transition metal compound used as the catalyst compositionin Examples 1 to 5 has better copolymerization properties than thecatalyst used in Comparative Examples 6 and 7, and 2,1-insersion wasincreased, and accordingly, the vinylene content was increased and thevinylidene content was decreased. However, in case of ComparativeExamples 6 and 7, the results showed that the vinylidene content was notdecreased.

In this regard, in view of viscosity change rate data, ComparativeExample 7 had a relatively low vinylidene content ratio but high totalamount of the number of unsaturated functional groups such as vinyl andvinylidene. Accordingly, viscosity change rate according to time waslarge, and through this, the stability at a high temperature may beexpected to be inferior.

On the contrary, in case of the copolymers of Examples 1 to 4, since thetotal amount of the number of unsaturated functional groups was smalland the ratio of vinylidene was low, the viscosity change rate wassmall, and in this case, the stability at a high temperature is expectedto be excellent.

In addition, if Example 3 and Comparative Example 6, which had the samedegree of the total number of unsaturated functional groups of 0.32/1000C, are compared, Example 3 which had a low R_(vd) value was confirmed toshow smaller viscosity change rate by about two times when compared withComparative Example 6 which had a high R_(vd) value.

Through this, it could be confirmed from the experimental data that theviscosity change is small in case where the total amount of theunsaturated functional groups is small as well as in case where theR_(vd) value is small.

1. An ethylene/alpha-olefin copolymer satisfying the following conditions i) to iv): i) viscosity: 6,000 cP to 40,000 cP, when measured at a temperature of 180° C., ii) molecular weight distribution (MWD): 1.5 to 3.0, iii) total number of unsaturated functional groups per 1000 carbon atoms: 0.8 or less, and iv) a R_(vd) value according to the following Mathematical Equation 1: 0.5 or less: $\begin{matrix} {R_{vd} = \frac{\lbrack{vinylidene}\rbrack}{\lbrack{vinyl}\rbrack + \lbrack{vinylene}\rbrack + \lbrack{vinylidene}\rbrack}} & \left\lbrack {{Mathematical}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$ in Mathematical Equation 1, the vinyl, vinylene and vinylidene mean the number of each functional group per 1000 carbon atoms, measured through nuclear magnetic spectroscopic analysis.
 2. The ethylene/alpha-olefin copolymer according to claim 1, wherein the density is 0.85 to 0.89 g/cc, measured according to ASTM D-792.
 3. The ethylene/alpha-olefin copolymer according to claim 1, wherein a weight average molecular weight is 17,000 to 40,000 g/mol.
 4. The ethylene/alpha-olefin copolymer according to claim 1, wherein the viscosity is 8,500 to 35,000 cP, when measured at a temperature of 180° C.
 5. The ethylene/alpha-olefin copolymer according to claim 1, wherein the R_(vd) value according to Mathematical Equation 1 is 0.3 or less.
 6. The ethylene/alpha-olefin copolymer according to claim 1, wherein the alpha-olefin comprises one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicocene.
 7. The ethylene/alpha-olefin copolymer according to claim 1, wherein the alpha-olefin is one or more selected from the group consisting of 1-buene, 1-hexene and 1-octene.
 8. The ethylene/alpha-olefin copolymer according to claim 1, wherein the alpha-olefin is comprised in an amount of from greater than 0 and 99 mol % or less, with respect to a total weight of the copolymer.
 9. The ethylene/alpha-olefin copolymer according to claim 1, further satisfying the following conditions v) to vi): v) a number average molecular weight (Mn): 9,000 to 25,000, and vi) Melt index (MI) at 190° C., 2.16 kg load by ASTM D1238: 200 to 1,300 dg/min.
 10. The ethylene/alpha-olefin copolymer according to claim 1, wherein the ethylene/alpha-olefin copolymer has a crystallization temperature (Tc) of 45° C. to 60° C., and a melting temperature (Tm) of 60 to 80° C., wherein both the crystallization temperature and the melting temperature are measured using a differential scanning calorimeter (DSC).
 11. A method of preparing the ethylene/alpha-olefin copolymer according to claim 1, comprising a step of polymerizing ethylene and an alpha-olefin-based monomer by injecting hydrogen in 45 to 100 cc/min in the presence of a catalyst composition including a transition metal compound of Formula 1:

wherein, R₁ is hydrogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; alkoxy of 1 to 20 carbon atoms; aryl of 6 to 20 carbon atoms; arylalkoxy of 7 to 20 carbon atoms; alkylaryl of 7 to 20 carbon atoms; or arylalkyl of 7 to 20 carbon atoms, R_(2a) to R₂ are each independently hydrogen; halogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; alkoxy of 1 to 20 carbon atoms; or aryl of 6 to 20 carbon atoms, R₃ is hydrogen; halogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; aryl of 6 to 20 carbon atoms; alkylaryl of 7 to 20 carbon atoms; arylalkyl of 7 to 20 carbon atoms; alkyl amido of 1 to 20 carbon atoms; aryl amido of 6 to 20 carbon atoms; or phenyl which is substituted with one or more selected from the group consisting of halogen, alkyl of 1 to 20 carbon atoms, cycloalkyl of 3 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms, alkoxy of 1 to 20 carbon atoms and aryl of 6 to 20 carbon atoms, R₄ to R₉ are each independently hydrogen; silyl; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; aryl of 6 to 20 carbon atoms; alkylaryl of 7 to 20 carbon atoms; arylalkyl of 7 to 20 carbon atoms; or a metalloid radical of a metal in group 14, which is substituted with hydrocarbyl of 1 to 20 carbon atoms; where among the R₆ to R₉, adjacent two or more are optionally connected with each other to form an aliphatic ring of 5 to 20 carbon atoms or an aromatic ring of 6 to 20 carbon atoms, wherein the aliphatic ring or the aromatic ring is optionally substituted with halogen, alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 12 carbon atoms, or aryl of 6 to 12 carbon atoms, Q is Si or C, M is a transition metal in group 4, and X₁ and X₂ are each independently hydrogen; halogen; alkyl of 1 to 20 carbon atoms; cycloalkyl of 3 to 20 carbon atoms; alkenyl of 2 to 20 carbon atoms; aryl of 6 to 20 carbon atoms; alkylaryl of 7 to 20 carbon atoms; arylalkyl of 7 to 20 carbon atoms; alkylamino of 1 to 20 carbon atoms; or arylamino of 6 to 20 carbon atoms.
 12. The method of preparing the ethylene/alpha-olefin copolymer according to claim 11, wherein the transition metal compound of Formula 1 comprises a compound represented by any one among the structures below:


13. The method of preparing the ethylene/alpha-olefin copolymer according to claim 11, wherein the catalyst composition further comprises a promoter for activating the transition metal compound of Formula
 1. 14. The method of preparing the ethylene/alpha-olefin copolymer according to claim 13, wherein the promotor comprises an organometal compound including a metal in group
 13. 15. The method of preparing the ethylene/alpha-olefin copolymer according to claim 13, wherein the promotor comprises one or more selected from a compound of the following Formula 2, a compound of the following Formula 3, or a compound of the following Formula 4: R₄₁—[Al(R₄₂)—O]_(n)—R₄₃  [Formula 2] in Formula 2, R₄₁, R₄₂ and R₄₃ are each independently any one selected from hydrogen, halogen, a hydrocarbyl group of 1 to 20 carbon atoms, or a halogen-substituted hydrocarbyl group of 1 to 20 carbon atoms, and n is an integer of 2 or more, D(R₄₄)₃  [Formula 3] in Formula 3, D is aluminum or boron, and each R₄₄ is each independently any one selected from halogen, a hydrocarbyl group of 1 to 20 carbon atoms, or a halogen-substituted hydrocarbyl group of 1 to 20 carbon atoms, [L-H]⁺[Z(A)₄]⁻ or [L]⁺[Z(A)₄]⁻  [Formula 4] in Formula 4, L is a neutral or cationic Lewis acid; H is a hydrogen atom, and Z is an element in group 13, and A is each independently a hydrocarbyl group of 1 to 20 carbon atoms; or a hydrocarbyloxy group of 1 to 20 carbon atoms, wherein the hydrocarbyl group or hydrocarbyloxy group is unsubstituted or substituted with one or more substituents selected from halogen, a hydrocarbyloxy group of 1 to 20 carbon atoms, or a hydrocarbylsilyl group of 1 to 20 carbon atoms.
 16. The method of preparing the ethylene/alpha-olefin copolymer according to claim 11, wherein the transitional metal compound of Formula 1 is in a supported state on a support, and the weight ratio of the transitional metal compound of Formula 1 to the support is 1:10 to 1:1,000.
 17. The method of preparing the ethylene/alpha-olefin copolymer according to claim 16, wherein the support is silica, alumina, magnesia or a mixture thereof.
 18. The method of preparing the ethylene/alpha-olefin copolymer according to claim 11, wherein the polymerization is performed at 80° C. to 200° C., and under about 1 to about 100 Kgf/cm². 